The present invention relates generally to receptacle connectors, and more particularly, to receptacle connectors that are used to make connections between an integrated circuit (xe2x80x9cICxe2x80x9d) package having numerous contacts, such as a BGA or LGA contacts, and a printed circuit board having numerous contacts pads formed thereon.
FIG. 7 illustrates a known connector having numerous terminals 300 embedded in an insulative housing 301. In use, the housing 301 is sandwiched between an IC package (not shown) and a printed circuit board 302. Each terminal 300 of the connector typically includes a contact arm 304 that is applied against a selected contact pad 303 of the circuit board 302, and a contact 305 integrally formed to the contact arm 304 for touching a selected counter contact, typically a spherical or land-shaped contact of the IC package. The connector housing 301 has retainers 306 formed therein which hold terminals 300 in the housing 301 in such a way that each contact 305 is resilient enough to yieldingly move, or sink, when applied to the counter contact.
The presence of these retainers 306 formed in or as part of the terminal housing 301 prevents reduction of the thickness of the connector housing. The known receptacle connector of FIG. 7 is too thick for use in notebook computers, which have been getting smaller and thinner. Also disadvantageously, this known connector allows its contact arm ends to be stained with flux in soldering to conductor pads 303. Also, soldering material is allowed to attach to its contact arm ends in the form of whiskers.
In the past, similar style connectors have been used to connect circuit boards together and they are also too thick for today""s thin and sleek computers. FIGS. 13 and 14 show an example of such a prior art connector, and in particular, FIG. 13 shows one terminal 1000 of the connector. A plurality of such terminals 1000 are mounted or press-fitted to a housing 2000 (FIG. 14) in order to complete an electrical connector 3000. Although only one terminal 1000 is shown in the figure, a plurality of such terminals 1000 are actually arranged side by side at the predetermined pitch. Referring to FIG. 6, the terminal 1000 includes a pair of contact members, or arms 1010, a press-fit portion 1020 formed at the base of the contact members, and a fixing portion 1030 formed adjacent the press-fit portion for connection to a solder ball 1040. The terminal 1000 is produced from a thin metal sheet by a stamping and forming process.
The terminal 1000 is received in a terminal receiving cavity (not shown) formed in the housing 2000 so that the press-fit portion 1020 may be press-fit against the inner wall of the terminal receiving cavity to hold the terminal 1000 in place. The solder ball 1040 is soldered to the fixing portion 1030 of the terminal 1000 and a portion of the solder ball 1040 opposite to the fixing portion 1030 externally projects from the housing 2000.
In FIG. 14, the mating connector 4000 is shown to include a dielectric housing 6000 having a plurality of contact pins 5000 mounted therein, which pins 5000 correspond to pairs of contact members of the terminals 1000 in the connector 3000 with one-to-one relation. The connector 3000 and the mating connector 4000 form a connector assembly. In general, each of the connectors 3000 and 4000 is mounted to their respective printed circuit boards so that they may be connected to each other via the connectors 3000 and 4000.
In addition to the terminal receiving cavity, as described above, another means for holding the terminal in the dielectric housing has been known in the art in which a terminal mounting channel is formed through the housing and a side edge of the terminal is latched to an opposite inner wall of the terminal mounting channel (see Japanese Patent Laid-Open No. 11-144821, for example).
These prior art connectors have a problem in that mounting of their terminals requires a number of assembly steps and thus adds cost to manufacturing because each terminals has to be press-fit to the terminal-receiving cavity or channel. In view of the recent tendency in electronics toward multi-pole configuration and higher terminal densities and with the advent of such design that not less than 100 terminals are arranged side by side at higher density, there is a strong need to solve the problem as above.
Furthermore, the prior art such terminal-receiving cavities or mounting channels formed in the housing create other problems such as when soldering the connector to the circuit board, wicking of either solder or solder flux may be produced via a clearance between the terminal and its cavity or channel, which may cause contamination to the contact members mated with the terminals of the mating connector.
In view of the above an object of the present invention is to provide an electrical connector having an improved configuration that reduces the manufacturing cost of the connector and eliminates the problem of solder or solder flux wicking.
Accordingly, it is a general object of the present invention to provide a circuit board connector of reduced thickness which utilizes solder balls on each side of its connector housing as electrical contacts.
Another object of the present invention is to provide a low-profile receptacle connector for BGA or LGA applications, the connector including a thin housing in the form of a socket, the socket having a plurality of cavities formed therein, a plurality of terminals disposed in the cavities, each of the terminals having a flat terminal body portion with at least two opposing edges, the terminal including a terminal retention arm extending in one direction from one of the two terminal body portion edges and a terminal retention stub extending in a second direction from the other of the two terminal body portion edges, the terminal flat body portion having shape that permits it to be held in place within a molding cavity such that molding material from which the connector housing is formed may flow around the terminal retention arm and stub to retain the terminal in place within the connector housing, thereby eliminating the need for forming terminal retainers in the connector housing associated with each connector housing cavity.
To attain such object an electrical connector for mounting to a printed circuit board, comprising a dielectric housing and a plurality of terminals arranged side by side at the predetermined pitch, is improved according to the present invention in that: each of the terminals includes a flat base portion, a pair of contact members formed from a first continuous folded-back portion that is folded back onto one side of the flat base portion, and a second folded back section bent transverse to the base portion, but extending on the opposite side of the base portion; the housing holds the terminals by performing an over-molding of the housing around the flat base portions of the terminals to form a generally flat plate-like housing; and the pair of contact members of the terminal extends toward one surface of the housing and the carrier coupling section extends toward the other surface of the housing.
According to one embodiment of the present invention, the pair of contact members of each terminal is disposed in a recess formed in said one surface of the housing.
According to another embodiment of the present invention, the other surface of the housing is provided with an opening leading to the terminal flat base portion, and the connector further includes solder balls soldered to the flat base portion via the openings and that externally project beyond the other surface of the housing.
According to further embodiment of the present invention, the terminal further includes a bent portion connecting between the flat base portion and the carrier coupling section, and a cut-out portion formed in the bent portion into which resin material that forms the housing, is permitted to flow, thereby anchoring the terminal base portion in place within the housing
According to another aspect of the present invention there is provided an electrical connector assembly, comprising: an electrical connector constructed in the manner as described above; and a mating connector comprising a plurality of contact pins each corresponding to each pair of contact members of the terminals with one-to-one relation, and a housing holding the contact pins by an over-molding of the housing around the contact pins to form a substantially flat plate-like housing.
According to one embodiment of the present invention one surface of the housing of the mating connector is provided with an opening leading to a base portion of the contact pin, and the mating connector further includes a solder ball soldered to the base portion via the opening and that is externally projected beyond said one surface of the housing.
An electrical connector according to the present invention is advantageous in the following points of view: Firstly, because of the configuration in which the housing is over-molded to the terminal consisting of the base portion, the pair of contact members and the carrier coupling section so that the terminal is held in the housing, there is no terminal press-fitting step required, and therefore, an efficient manufacturing process can be realized even for the electrical connector having an increased number of terminals. Furthermore, because of no clearance that extends through the housing between the housing and terminal, there is no possibility of any rising action of solder or solder flux occurred during the soldering operation on the printed circuit board.
Secondly, because the pair of contact members of the terminal are confined in a recess of the housing, the pair of contact members are protected by the housing against any deformation or contamination thereto.
Thirdly, because of the solder ball soldered to the base portion of the terminal and externally projected from the housing, a connector of ball grid array (BGA) type is provided. Alternatively, a connector of pin grid array (PGA) type in which a pin-like solder tail for DIP soldering or a solder tail for surface soldering (SMT) may be provided on the carrier coupling section of the terminal may be provided within the scope of the present invention.
Fourthly, because of the presence of a bent portion between the base portion and the carrier coupling section, a cut-out portion is formed in the bent portion, which assists in reducing the distance (or pitch) between adjacent terminals of the connector as much as possible. This is very suitable for smaller pitch arrangement of the terminals.
Fifthly, because the mating connector also has the same configuration in which its own dielectric housing is over-molded to a number of contact pins, there is provided the electrical connector assembly having a capability of easily and efficiently mating the electrical connector with the mating connector. Such connector assembly eliminates any possibility of rising action of solder or solder flux during the process of mounting the connector to the circuit board.
Sixthly, the mating electrical connector may be an electrical connector of BGA type.
These and other objects, features and advantages of the present invention will be clearly understood through a consideration of the following detailed description.